1. Field of the Invention
The present invention relates to a load drive circuit such as a low-side driver, high-side driver, or motor driver, which is constructed from a typical electric/electronic circuit and is built into an electronic control device and which has a function of checking the operation of a diagnostic circuit for diagnosing the condition of a load.
2. Background Art
Some conventional load drive circuits such as a low-side driver, high-side driver, or motor driver that are constructed from typical electric/electronic circuits have circuits that diagnose the condition of a load being driven. Such a diagnostic circuit judges the condition of the load by monitoring the output voltage of the load, the current flowing through the load, or the like while the load is being driven or not driven. The operation of such load drive circuit with a diagnostic function is checked by executing the diagnostic function while the load is being driven or not driven. However, in order to check the diagnostic circuit, it is necessary to operate the drive circuit by putting it in a disable state, which is different from a normal mode, and by checking whether or not the diagnostic circuit can diagnose the condition of the load.
However, once a load drive circuit has been built into an electronic control device including a load, it is impossible for a diagnostic circuit of the load drive circuit to detect an abnormality of the load within the control device unless the load actually has an abnormality. Therefore, establishing a method for checking the operation of the diagnostic circuit after it has been built into the control device is an object to be achieved.
Reference 1 (JP Published Patent Application No. 11-13519 A (1999)) discloses a method of creating an abnormal state by actually turning off only a power supply of a load within an electronic control device, in order to check the operation of a diagnostic circuit. Reference 2 (JP Published Patent Application No. 2002-257668 A) discloses a method of running a control device on a simulator and creating an abnormal state on the simulator. However, since these methods create abnormal states in an artificial manner, there is a problem in that the operation of the diagnostic circuit cannot be checked after it has been built into the control device and is actually used.